http://www.progesoft.com/ or http://www.cadopia.com/ is about $200-$350 and is probably the best cheap autocad clones.
They are based on the same intellicad CAD library with different front ends. They read/write Autocad and have the same Autocad commands

In fact intellicad does a better job of reading DXF than Autocad - we use it to translate bad DXF files from some GIS apps